Radio receiving system



Oct. 18, 1932. s. COHEN RADIO 'HEGEIVINGASYSTEM Filed Feb. 17, 1925 JNVENToR @M/! z,

ATTORNEY Patented Oct. `18, 1932 4UNITED STA SAMUEL COHEN, OF BROOKLYN, NEW YORK,

CORPORATION, OF NEW YORK, N.

AssIGNoR To GENERAL INSTRUMENT Y.; A CORPORATION or NEW-YORK RADIO RECEIVING SYSTEM Application iled February of my invention is to provide an electron tube Vamplification system,

which may include a large number of stages of amplification for increasing feeble electrical energy toenergy at large amplitude without interference arising fromk the oscillatory currents in the several amplification circuits.

. Another `Object lof my invention is toprovide an electron ktube amplification system wherein. selected stages of amplification may be equipped with supplemental circuits op-y erating to eliminatethe effect of undesired oscillatory currents upon a desired signaling vfrequency during its passage through the amplication system.

Still another object of myinvention vis to provide a supplemental circuit arranged for connection to the circuits of .electron tube' amplification systems whereby undesired oscillatory currents may be absorbed from the system and dissipated in the form of eddy current or hysteresis losses, in such manner that the undesired oscillatory currents will have no effect upon the signaling currents.

A further obj ect of my invention is to provide an impedance circuit which may be con-` nected with the circuits of an electrontube amplication system forregulating the input impedance of the electron tube for shifting the phase relationship of the voltages across the grid and plate circuits in such manner that the oscillatory currents in the ampliicas tion system are substantially eliminated.

A still further object of my invention is the provision of an impedance circuit arranged to be so connected with theelectrodes of electron tubes in an amplification system that the phase relationship of the voltages across the input and output circuitsl ofeach of thek tubes may be regulated to be slightly less than 180 degrees, whereby the amplification circuits are rendered stable andf arenot affected by undesired oscillatory currents.

VMy invention resides in the location of an v1v, 1925. serial No. 9,753.

impedance circuit with respectto the input L and output circuits of an electron tube in an amplification system which includes an in-V ductance in the input circuit' of the electron tube system or an inductance `equivalent thereto, whereby regulation 'of the phase of the voltages existing across the input 'and output circuits of the tube may be secured independent of the frequency ofthe incoming signaling energy.

My invention finds particular application in radio frequency yamplification lcircuits where it is desired to amplify signaling currents overl a broad bandof frequencies. Heretofore in the art it has been proposed tobalance or neutralize the capacity couplingbetween the electrodes of the .electron tubes in an amplification system and for this purpose values ofvinductance and lcapacityhave been connected with the circuits of-electron tubes in the amplifier for balancing the effects of the intra-electrode capacities within the electron tubes.- This ,method of balancing capacity coupling has been dependent upon the particular values of capacity couplingL between the electrodes ofthe electron tubes an accordingly directly vdependent upon `the characteristics of the electron tubes in the system. lManufacturers of electron tubes have departed from the established characteristics of tubeconstruction with the result that circuits designed to'eliminate capacity coupling in a multistage amplifier have failed to function. By my present invention I increase the flexibility of the amplification circuit to the extent that tubes of widely diiferent characteristics may be employed and the impedance circuits supplementing the circuits of the electron' tubes readily adjusted to shift the phase relationship of the voltages in the input andoutput circuits of the tubes for the elimination of oscillations in the amplification system.v f y y l My invention will be moreclearly understood fromthe specification hereinafter following, by reference to the accompanying drawing, wherein: V

Figure 1 is a theoretical diagram illustratingthe intra-electrode capacities within anelectron tube; Fig. 2 isa theoretical diagram illustrating the connections which I provide for the impedance circuit between the input and output circuits of the electron tube amplification system; Fig. 3 illustrates an application of my invention to a radio frequency amplification system in a radio receiving apparatus; Fig. 4 illustrates the application of my invention to a multistage radio frequency amplifier in connection with a detector circuit for a radio receiving apparatus; and Fig. 5 shows an application of the impedance circuit of my invention connected with respect to a single stage of radio frequency amplification preceding a detector circuit in a radio receiving system.

By the employment of the impedance circuit arrangement illustrated in the drawing, I have successfully operated multistage radio frequency amplifiers wherein the limitation as to the number of stages which may be employed depends not upon the electrostatic coupling between the electrodes of the electron tubes in the system, but directly upon. the magnetic coupling of the interstage cou'- pling transformers. The shielding of the coupling transformers either magnetically or electrostatically eliminates this undesired coupling effect. The values of the impedance circuit which I provide as supplemental connections between the input and ouput circuits of the electron tubes are so proportioned with respect to the value of the inductance in the input circuit, or the equivalent of such inductance, that the phase of the voltage relation between the grid and plate circuits is shifted so that the phase relationship is slightly less than 180 degrees. In this condition the circuits become stable and oscillatory currents are eliminated. 'Ihe phase relationship may be controlled for tubes of different characteristic for modifying the values of the resistance, capacity and inductance included in the impedance circuit until that point is found at Ywhich interfere-nce due to oscillatory currents is eliminated. By shifting the phase ofthe voltages between the input and output circuits of the tubes, the resulting voltage which normally directly excites the tube cirn cuits intooscillation, becomes substantially nil and correspondingly the current is .so infinitesimal that oscillatory currents are practically absent from the tube circuits.

Referring more particularly tothe drawing, VFigure 1 represents the distribution of the intra-electrode capacities within an electron tube wherein the letters G, P and F, designate the grid, plate and filament, respectively. The inherent Ycapacity existing between lthe grid and plate electrodes has been designated'by reference characters GCP. The inherent capacity existing between'the filament electrode and the plate has been designated by the reference characters F CP, and lilewise'the inherent capacity existing between the grid and the filament has been designated by the reference characters GCF.

In Fig. 2 these inherent capacities have been illustrated by circuit diagram wherein an input circuit containing inductance 1 is coupled to an inductance 2 which is connected across the terminals 3 and 4 of the capacity system. The output circuit of the system includes an inductance 5 and a source of high potential energy designated at 6, the inductance 5 being coupled with the inducta-nce system 7. An impedance circuit 8 is provided connected to a variable contact 9 along inductance 2 and to the point 10 in the capacity system. A shunt pathinductance L3 of the input inductance L1, indicated by reference character 2, is provided between the point 3 and point 10 in the capacity system of the impedance circuit V8. The inductance L3 must be apportioned with such relation with` regard to the impedance circuit 8, that the phase relationship of the grid and plate current is slightly less than 180 de grees. The impedance circuit may include a variable resistance and capacity. It is to be noted that the resistance in this impedance circuit is used primarily for the purpose of changing the 180 degree phase relationship. provided that the circuit which includes the impedance circuit contains the tube capacities of the corresponding inductances, that is in Figure 2, the value of inductance the value of impedance 8 and the Value of capacity GCP.

In Fig. 8 a practical application of my invention is illustrated at a radio receiving station employing Athe antenna ground, system 11 and 14, including the primary winding 12 in circuit therewith. Secondary inductance 15 is coupled with =the primary winding 12 and is tuned by varia-ble condenser 16 to the incoming signaling frequency. The electron tube 17 functions as a radio frequency amplifier having primary inductance 18 in the output circuit thereof. The impedance circuit is illustrated as comprisA ing capacity 19 and resistance 20, both of whichmay be adjustable to enable the circuit to cooperate with electron tubes of different characteristics. The secondary inductance 15 has a portion thereof indicated at L3 and included in circuit with the adjustable impedance 8. The radio frequency amplifier has its output circuit coupled with the secondary inductance 21 which is tuned by condenser 22. This circuit connects with the detector tube 24, including grid leak and grid condenser 23. A responsive device 25 is shown connected in the output circuit of the detector tube 24. The cath'odes of the several tubes are heated from battery 27 while the plate potential for the tubes is supplied from battery 26. A by-pass condenser 28 is provided in the output circuits. The value of inductance L3, capacity 19 and resistance 20 Y tube 17 while an additional impedance circuit, comprising condenser 29 and resistance 30, is also connected in circuit with the inductanceL3 from a point in theinput circuit of electron tube 31 forming the second sta-ge of radio frequency amplification. tance Lain the output'circuit of tube 17 in the circuit arrangement illustrated Fig. 4 is equivalent to the inductanceL3 consisting of a portion of the secondary winding -15 in Fig.

. 3. The inductance L3 kin this instance constitutes'the primary winding of the coupling transformer which is associated with secondary winding 33 functioning to transfer the energy to the second stage of radio frequency amplification formed by tube 31. The secondary winding 33 is tuned by variable condenser 32 and the output energy delivered through winding 34: to aA detector circuit as hereinbefore described. It will be observed that the phase of the input and outputk currents in the electron tubes 17 and 31 is displaced by control means independent of frequency and each of the impedance circuits being adjustable permits the amplification syss tem to function efficiently with tubes of widely different characteristics.

In F ig. 5 I have shown the impedance circuit 8 associated with a single stage of radio frequency amplification and connected between a point 35 in the input circuit of the radio frequency amplification circuit connected with tube 17 and the lower terminal of inductance L3 in the output circuit of the radio frequency amplification system. The impedance circuit in this relationship operates, as hereinbefore described, to shift the phase relationship of the input and output voltages stabilizing the radio frequency amplifier independent of the operating frequency. It will be observed that the principle which I employ of shifting the phase relationship of the input and output currents is applicable to radio frequency amplification systems independent of tube characteristics and the operating frequency. rIhese factors permit wide application of the invention to electron tube circuits and, accordingly, the applications of the invention described herein are to be considered in the illustrative sense rather than the limiting sense. It will also be understood that modifications of my inven- The induci tion may be made and that I intend no limita-- tions upon the invention other than `are imposed by tlie scope of the appended claims.

What I'claim and desireto securebyLetters Patent of the United States is as follows 1. An amplification system comprising in C combination a plurality of electron tubes, each having grid, cathode and plate electrodes, a tuned input and an output circuit interconnecting said electrodes, means inter-linking the outputcircuit of one of said electron tubes with the input circuit of a succeeding electron tube, and an impedance circuit connected between points on the grid sides of 'said tuned input circuits of succeeding elecn tron tubes rand a point in the output circuit "t of each of said electron tubes for stabilizing the operation of said amplification system.

2. An amplification system comprising in combination a plurality of electron tubes, each having grid, cathode and plate electrodes, in- "'i" put and output circuits interconnecting said electrodes, means inter-linking the output circuit of one of said electron tubes with the grid sidesof the input circuit of a succeeding elect tron'tube, an impedance circuit arranged for connection between points in the input cii-` cuits of succeeding electron tubes and including an element in the output circuit of each of said electron'tubes for stabilizing 'the operationof said ainplication system.

` 3. .An amplification system comprising in combination a plurality of eiectron tubes, each having grid, cathode and plate electrodes, input and output circuits interconnecting said electrodes, means inter-linking the output circuit of one of said electron tubes with the input circuit of asucceeding electronV tube, and an impedance circuit coinprising a plurality of adjustable elements connected between pointson the grid sides of the input circuits of succeeding electron tubes with a connection between a midpoint in said impedance circuit with a point in the output 'circuit of` one of said electron tubes for stabilizing the operation of said amplification system. I l

4. An amplication system comprising in combina-tion a plurality of electron tubes, each having grid, cathode and lplate electrodes, input vand output circuits interconnecting said electrodes,` means inter-linking the output circuit of one of said electron tubes with the input circuit of a succeeding electron tube,` an impedance circuit including a plurality of similar elements connected in series with the extremities of the impedance circuit connected to points on the grid sides of thev vinput circuits of succeeding electron tubes,

and a connection from the midpoint between "a pair of said similar elements in said im- 5. An amplification system comprising in combination a plurality of electron tubes, each having grid, cathode and plate electrodes, input and output circuits interconnecting said electrodes, means inter-linking the output circuit of one ot said electron tubes with the input circuit of a succeeding electron tube, and an impedance circuit including a plurality of .adjustable elements connected in series with each other and connected with the grid sides of the input circuits of succeeding electron tubes, a connection at a point midway between said adjustable elements in said impedance circuit and a point in said output circuit for stabilizing the operation of said amplification system.

6. An amplification system comprising in combination a plurality of electron tubes, each having grid, cathode and plate electrodes, input and output circuits interconnecting said electrodes, means inter-linking the output circuit of one of said electron tubes with the input circuit of a succeeding electron tube, an impedance circuit having its opposite terminals connected with points on the grid sides of the input circuits of succeeding electron vtubes with a connection from the divided portion of said impedance circuit with a point in the output circuit of one of said electron tubes for stabilizing the operationof said amplification system.

7 An amplification system comprising in combination a plurality of electron tubes, each having grid, cathode and plate electrodes, input and output circuits interconnecting said electrodes, means inter-linking the output circuit of one of said electron tubes with the input circuit of a succeeding electron tube, and supplemental means inter-linking the input circuits of succeeding electron tubes comprising a plurality of impedance elements with a midpoint connection between said impedance elements and a point in the output circuit of adjacent electron tubes for stabilizing the operation of said amplification system.

8. An amplification system comprising in combination a plurality of electron tubes, each having grid, cathode and plate electrodes, input and output circuits interconnecting said electrodes, means inter-linking tlie output circuit of one of said electron tubes with the input circuit of a succeeding electron tube, an impedance circuit containing a plurality of resistance and capacity elements with the extremities of said circuit connected to points on the grid sides of the input circuits of succeeding'electron tubes, and a connection between a midpoint in said impedance circuit and a point in the output circuit of said electron tubes Jfor stabilizing the operation of said ampliiication system.

9. An amplication system comprising in combination a plurality of electron tubes, each having grid, cathode and plate electrodes, input and output circuits interconnecting said electrodes, means inter-linking the output circuit of one of said electron tubes with the input circuit of a succeeding electron tube, an impedance circuit comprising a plurality of resistance and capacity elements connected in series with the opposite terminals of said circuit connected with said capacity elements and with points in the input circuits of succeeding electron tubes, said resistance elements being mutually interconnected to each other and to the opposite terminals of said capacity elements, and a connection between said resistance elements and a point in the output circuit of one of said tubes for stabilizing the operation of said amplification system.

10. An amplification system comprising in combination a plurality of electron tubes, each having grid, cathode and plate electrodes, input and output circuits interconnecting said electrodes, means inter-linking the output circuit of one of said electron tubes with the input circuit of a succeeding electron tube, and a balanced impedance circuit including resistance and capacity units electrically connected in series with the opposite terminals of said impedance circuit connected to points on the grid sides of said input circuits ot succeeding electron tubes, and a connection between a midpoint in said impedance circuit between said resistance and capacity units with points in the output circuits of said electron tubes for stabilizing the operation of said amplification system.

SAMUEL COHEN. 

